There’s a 10,000 sf lot off of Sparta that’s been listed for $399K. It’s really the backyard of a house, and they split the lot and sold of the house separately with just a small space around the back.
To access the lot, you have to go up a private driveway.
I think it’s still on the market.
Of course, a more desirable lot would be worth a bit more, but I would guess around $300K-$500K right now. If it’s at the top of a hill, and not so close to the RR tracks, it might be worth a bit more.
IMHO, land value is and will be going down. If your friend wants to sell, it would be a good time to do so now.